Method and apparatus for offload operation of the idle mode in a cellular device

ABSTRACT

A dormant/idle mode operation of a plurality of cellular device(s) is offloaded using proximity radio interface to a second device having cellular capability so that a plurality of cellular devices can turn off the radio and baseband circuitry associated with the cellular capability, and save battery power. The second device to which the dormant/idle mode operation is offloaded acts like a proxy device for a plurality of cellular devices to perform at least one of the following functions on behalf of plurality of cellular devices: monitor network page, perform cell re-selection, perform tracking area update, or perform D2D transmission and reception, wherein the second device and the plurality of cellular devices are connected each other through a proximity radio interface.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application is a continuation of application Ser. No. 15/243,930,which claims priority to Indian Provisional application No.902/KOL/2015, filed on Aug. 21, 2015, in the Indian Patent Office, theentire disclosures of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure broadly relates to the field of cellularcommunication and more specifically related to offload of dormant/idlemode operation from a first cellular device to a second cellular deviceso that the second cellular device acts as a proxy for the firstcellular device.

BACKGROUND

There is huge growth in a number of smart devices such as smartphones,tablets, smartwatches, wearables etc. in different parts of the world.These smart devices have at least one radio capability such asBluetooth/WiFi, or cellular capability like the third generation (3G)based on universal mobile telecommunication systems/code divisionmultiple access (UMTS/CDMA) or the 4^(th) generation (4G) based on longterm evolution (LTE)/WiMAX etc. With one or more radio capabilityequipped on such smart devices, the one or more radio capabilityequipped on such smart device are able to connect to the internet togain access to multitude of applications like audio/video streaming,navigation maps, social networking applications, games and plethora ofover the top (OTT) services/applications in addition to operator/serviceprovider services. Further, from user perspective ownership of suchsmart device is not restricted to one type of smart device where a userowns a smartphone, a smartwatch, a tablet or simply a group of devicesare always present in the vicinity of the user. When the user is on themove both the operator/service provider services and the OTT servicesare available on the smart device through the cellular radio interfaceunless the user is travelling in car/bus/train where he can connect tothe wireless LAN (WLAN) access point (AP) to gain access to OTTservices.

Similarly, typically when the user is in home environment or officeenvironment or any public place equipped with WLAN AP then WiFi basedradio capability is used for accessing the OTT services on the smartdevice. In such cases, the operator/service provider services like voicecalls, SMS etc are delivered through the cellular capability on thesmart device. However, the cellular radio of the smart device may be indormant/idle mode when there is no active session ongoing on thecellular interface in order to save battery power. Most personalcomputing devices have proximity connectivity capability likeBluetooth/WiFi to pair/associate with another smart device likesmartphone, tablet etc. Such dormant/idle mode power consumption can befurther minimized based on the methods disclosed in the inventionwherein the dormant/idle mode operations of a first smart device areoffloaded to a second smart device through a proximity interface such asBluetooth/WiFi. The second smart device having cellular radio capabilityacts as a proxy for the first smart device to carry out one or moredormant/idle mode functions on behalf of the first device in addition tosimilar functions for the second smart device.

The first smart device referred above is not restricted to smartphone ortablet but could also cover wearable device like smartwatch, healthbands, smart glasses, smart necklaces, etc. The second smart devicereferred above is not restricted to smartphone or tablet but could alsocover WLAN AP having cellular capability for backhaul, electronicconsoles/dashboards inside cars/bus/train having WiFi capability forproximity connectivity and cellular capability for backhaul. Even thoughthe invention is illustrated in detail referring to wearable kind ofdevice as the first smart device and smartphone kind of device as thesecond smart device the scope of the invention is equally applicable forthe various categories of the first smart device and second smart deviceas the aforementioned. The description of the invention referring towearable kind of device as the first smart device and smartphone kind ofdevice as the second smart device may not be considered as limiting casefor the applicability of the invention. The proximity radio capabilitymentioned above based on Bluetooth and/or WiFi through which the firstsmart device and the second smart device are paired/associated may notbe considered as restrictive for the applicability of the inventionbecause the proximity interface may also be LTE based ProSe interface.However, for simplicity the invention is illustrated based onBluetooth/WiFi proximity interface since these are dominant interfacesseen in the field worldwide.

SUMMARY

The cellular radio in dormant/idle mode of a smart device would normallyjust monitor network page for mobile terminated calls, perform cellre-selection to support dormant/idle mode mobility, perform locationupdate when triggered by non-access stratum (NAS) layer of the cellularradio so that network can keep track of the smart device for paging andmay transmit or receive ProSe direct communication (D2D operation). Eventhough the smart device cellular radio is in dormant/idle modeperforming very few basic operations like monitoring paging, cellre-selection, tracking area update etc., there is some amount of batterypower consumed.

The dormant/idle mode power consumption can be further minimized basedon the methods disclosed in the invention wherein the dormant/idle modeoperations of a first smart device are offloaded to a second smartdevice through a proximity interface such as Bluetooth/WiFi. The secondsmart device including cellular radio capability acts as a proxy for thefirst smart device to carry out one or more dormant/idle mode functionson behalf of the first device in addition to similar functions for thesecond smart device.

When the first smart device has offloaded one or more dormant/idle modefunctions to the second smart device then the cellular radio capabilityof the first smart device can be completely switched off but theproximity radio capability like Bluetooth/WiFi is active. The firstsmart device and the second smart device are paired/associated with eachother through the proximity radio capability so that the second smartdevice can transfer the dormant/idle context back to first smart devicein case of network page and/or refresh of NAS security context for thefirst smart device.

The following aspects with the offload of one or more dormant/idle modefunctions from the first smart device to the second smart device areaddressed in the disclosed invention: Smart device Identity sharing,PLMN selection, Cell re-selection, Tracking area update and ProSe directcommunication (D2D operations) in idle mode.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIGS. 1A and 1B illustrate an offload of one or more dormant/idlefunctions using proximity radio interface from a plurality of firstsmart devices including cellular radio capability to a second smartdevice including cellular radio capability according to one embodiment.

FIG. 2 illustrates a message sequence flow for an offload ofdormant/idle mode operation according to one embodiment.

FIG. 3 illustrates a message sequence flow for a offload of dormant/idlemode operation according to another embodiment.

FIG. 4 illustrates a message sequence flow for a network controlledoffload of dormant/idle mode operation according to one embodiment.

FIG. 5 illustrates a tracking area update procedure on behalf of aplurality of first smart devices that includes offloaded dormant/idlemode operation according to one embodiment.

FIGS. 6A and 6B illustrate a tracking area update procedure on behalf ofa plurality of first smart devices that includes offloaded dormant/idlemode operation according to another embodiment.

FIGS. 7A and 7B illustrate a paging monitoring procedure on behalf of aplurality of first smart devices that includes offloaded dormant/idlemode operation according to one embodiment.

FIG. 8 illustrates actions taken on detecting an event trigger for firstsmart device according to one embodiment.

FIGS. 9A and 9B illustrate one or more idle mode functions performed onbehalf of a plurality of first smart devices by a second smart device inactive/connected mode according to one embodiment.

FIGS. 10A and 10B illustrate a flow chart for a user equipment (UE)operations for a first smart device when one or more idle mode functionsare offloaded to a second smart device according to one embodiment.

FIGS. 11A, 11B and 11C illustrate a flow chart UE operations for asecond smart device when one or more idle mode functions are offloadedfrom a first smart device according to one embodiment.

FIG. 12 illustrates a block diagram of a first smart device or a secondsmart device.

DETAILED DESCRIPTION

FIGS. 1 through 12, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged electronic device.

FIGS. 1 through 12, discussed below, and the various embodiments of thepresent disclosure used to describe the principles of the presentdisclosure in this patent document are by way of illustration only andshould not be construed in any way to limit the scope of the disclosure.Those skilled in the art will understand that the principles of thepresent disclosure may be implemented in any suitably arrangedcommunication technologies. Hereinafter, operation principles ofexemplary embodiments of the present disclosure will be described indetail with reference to accompanying drawings. In the followingdescription of the present disclosure, a detailed description of knownconfigurations or functions incorporated herein will be omitted when itis determined that the detailed description may make the subject matterof the present disclosure unclear. Terms described later are defined inconsideration of the functions of the present disclosure, but may varyaccording to the intention or convention of a user or operator.Therefore, the definitions may be made based on contents throughout thespecifications.

FIG. 1A illustrates an offload of one or more dormant/idle functionsusing proximity radio interface from a plurality of first smart devicesincluding cellular radio capability to a second smart device includingcellular radio capability. FIG. 1A depicts the cellular networkenvironment 100 where several smart devices are connected to thecellular network 103. A plurality of first smart devices 101 a, 101 b,101 c so on and so forth are connected to the cellular network 103 usingtheir cellular radio capability through the cellular radio interface 104a, 104 b, 104 c respectively. A second smart device 102 is alsoconnected to the cellular network 103 using its cellular radiocapability through the cellular radio interface 104 d. The cellularnetwork 103 comprises of a plurality of network nodes like the eNodeBs(eNBs) responsible for radio functions, mobility management entity (MME)responsible for control functions like session and mobility management,data gateways like serving gateway (SGW) and PGW responsible for routingdata packets between the eNB and the external network. For the sake ofexplanation of disclosed invention the cellular network 103 is assumedto be long term evolution (LTE) based comprising the evolved universalterrestrial radio access network (E-UTRAN) and evolved packet core(EPC). The disclosed invention is also applicable to cellular networkbased on universal mobile telecommunications system (UMTS) by extendingthe disclosed methods in the context of procedures relevant foruniversal terrestrial radio access network (UTRAN).

The plurality of first smart devices 101 a, 101 b, 101 c so on and soforth may be connected to the second smart device 102 using theirproximity radio capability through the proximity radio interface 105 a,105 b, 105 c respectively. For the sake of explanation of disclosedinvention the proximity radio interface 105 a, 105 b, 105 c is assumedto be Bluetooth or WiFi based having a range of few meters to severaltens of meters. The disclosed invention is also applicable if theproximity interface is LTE based using the ProSe interface.

FIG. 1B illustrates the network environment 100 wherein it is assumed aplurality of first devices 101 a, 101 b, 101 c including cellular radiocapability and proximity radio capability and the second smart device102 also having cellular radio capability and proximity radio capabilitybelong to the same registered public land mobile network (PLMN). Whenthe smart devices 101 a, 101 b, 101 c and 102 are in the vicinity ofeach other either in a stationary environment like home/office ormobility environment like car/bus/train these devices perform one ormore dormant/idle mode functions like monitoring paging, cellre-selection, tracking area update when triggered by NAS layer, maytransmit or receive ProSe direct communication (e.g., D2D operation)independently. Since all the devices are in the same vicinity and belongto the same PLMN the dormant/idle mode functions like cell re-selectionand tracking area update may be triggered at more or less similar timeinstances for majority of the devices. Since the devices are performingindependent functions using the cellular radio capability the devicesconsume battery power to perform those functions.

Further, it is possible that a first smart device 101 a may be connectedto second smart device 102 when in vicinity for most of the time. Suchscenario is possible if first smart device 101 a is a smartwatch orwearable and the second smart device 102 is a smartphone belonging tothe same user. In such scenario the dormant/idle mode power consumptionof first smart device 101 a can be further minimized based on themethods disclosed in the invention wherein one or more dormant/idle modefunctions of a first smart device 101 a are offloaded to a second smartdevice 102 through a proximity interface such as Bluetooth/WiFi. Thesecond smart device 102 including cellular radio capability acts as aproxy for the first smart device 101 a to carry out one or moredormant/idle mode functions on behalf of the first smart device 101 a inaddition to similar functions for the second smart device. When thefirst smart device 101 a has offloaded one or more dormant/idle modefunctions to the second smart device 102 then the cellular radiocapability of the first smart device 101 a can be completely switchedoff but the proximity radio capability like Bluetooth/WiFi is active.This would result in significant power saving for the first smart device101 a. The power consumption of second smart 102 may be marginallyincreased since the second smart device 102 acts a proxy for first smartdevice 101 a. However, the second smart device 102 may have superiorcapability in terms of battery source compared to smart device 101 a sothe additional marginal power consumption for the proxy function may notadversely impact the power consumption of second smart device 102.

In another scenario, the second smart device 102 can be a WLAN APincluding cellular radio capability as the backhaul to connect to thenetwork typically seen in home or office environment. In such scenariothe dormant/idle mode power consumption of a plurality of first smartdevices 101 a, 101 b, 101 c can be further minimized based on themethods disclosed in the invention wherein one or more dormant/idle modefunctions of a plurality of first smart devices 101 a, 101 b, 101 c areoffloaded to a second smart device 102 through a proximity interfacesuch as WiFi. This would result in significant power saving for theplurality of first smart devices 101 a, 101 b, 101 c. The powerconsumption of the second smart device 102, if WLAN AP is not a majorconcern , is permanently connected to power source. However, in suchscenario, the second smart device 102 may experience slightly increasedprocessing load since the second smart device 102 acts as proxy for aplurality of the first smart devices. The second smart device 102 mayhave superior capability in terms of processor power compared to smartdevices 101 a, 101 b, 101 c because of the larger form factor of thesecond smart device 102 if the second smart device 102 is WLAN AP so theadditional processing load for the proxy function may not adverselyimpact the processing capability of the second smart device 102. In anembodiment the second smart device can be a multi subscriber identitymodule (SIM) device. In an embodiment the second smart device uses theprotocol stack corresponding to SIM from a plurality of SIMs such thatthe PLMN selected by the second smart device is same PLMN as the firstsmart device. In an embodiment a multi SIM second smart device may behandling dormant/idle operations of one or more first smart devices on afirst SIM and handling one or more first smart devices on a second SIMand so on.

FIG. 2 illustrates a message sequence flow 200 for an offload ofdormant/idle mode operation from a first smart device (101) to a secondsmart device (102). At step 201,the second smart device (102) may beeither in dormant/idle mode or active/connected mode from the cellularradio interface perspective. At step 201 b, the first smart device (101)is in dormant/idle mode from the cellular radio interface perspective.At step 202, the first smart device (101) connects to the second smartdevice (102) for example based on Bluetooth connection set-up andpairing. When the proximity radio (i.e. Bluetooth radio) in the firstsmart device (101) and the second smart device (102) is activated, thenthe first smart device (101) may send discovery signal for Bluetoothdevices in the proximity and on detecting the second smart device (102),the association protocol between the first smart device (101) and thesecond smart device (102) establish the proximity connectivity betweenthe proximity radios of the paired smart devices. This establishment ofassociation between the proximity radios of two devices based onBluetooth protocol is called pairing. During the pairing procedure thefirst smart device (101) and the second smart device (102) may mutuallyauthenticate each other if the first smart device (101) and the secondsmart device (102) are trusted partners to establish the securedproximity link. After pairing the devices, the two associated proximityradios of the two devices are allowed to transfer data using the securedproximity interface for any application specific exchange of informationusing Bluetooth protocol.

In another example such secured proximity link between the first smartdevice (101) and the second smart device (102) can also be establishedusing WiFi protocol. At step 203, the first smart device (101) intendsto offload dormant/idle operation to the second smart device (102) andtherefore request for PLMN information concerning the PLMN on which thesecond smart device (102) is registered. The PLMN information isrequested on the proximity interface using the protocol associated withproximity radio interface. This means the contents of the requestmessage are transparent to proximity radio and can be considered asapplication data from proximity radio perspective such that PLMN requestis in a container regardless of the proximity protocol used.

The PLMN selection for the first smart device (101) and the second smartdevice is in accordance to PLMN selection procedures specified in 3GPPTS 23.122. At step 204, the second smart device (102) provides itsregistered PLMN information and optionally UE identity of the secondsmart device to the first smart device (101) through the securedproximity interface. At step 205, the first smart device (101) verifiesthe registered PLMN of the second smart device (102) and if the firstsmart device (101) and the second smart device (102) match with thefirst smart device (101) and the second smart device (102) ownregistered PLMN then in steps 206, 207 and 208 the first smart devicesends dormant/idle mode offload indication along with assistanceinformation in the form of offload request container. The offloadindication messages shown in step 206 and step 208 are inter-radiomessages within the first smart device and the second smart device.These inter-radio messages are information exchanged between thecellular radio and proximity radio within the smart device which istransparent from the perspective of proximity radio and can beconsidered as application data.

The exchange of inter-radio messages between the cellular radio andproximity radio within the smart device involves co-ordination betweenthe cellular radio and proximity radio which could be handled by a RadioInterface Layer. The proximity radio acts as relay to transmit orreceive the inter-radio message on the proximity radio interface. Atstep 209, the second smart device (102) accepts the offload request fromthe first smart device (101) and therefore sends the offload acceptresponse at step 210. With the reception of inter-radio message offloadcomplete at step 211 the first smart device (101) has successfullyoffloaded one or more idle mode functions to the second smart device(102). The various steps mentioned in FIG. 2 illustrates the generalizedprocedure for offload of dormant/idle mode operation from the firstsmart device to the second smart using the proximity radio interface;therefore either some of the steps can be combined, sequence of somesteps can be modified or some steps can be omitted without deviatingfrom the spirit of the illustrated procedure.

FIG. 3 illustrates a message sequence flow 300 depicting an alternativemethod for the offload of dormant/idle mode operation from a first smartdevice (101) to a second smart device (102). At step 301, the secondsmart device (102) may be either in dormant/idle mode oractive/connected mode from the cellular radio interface perspective. Atstep 30,1 b the first smart device (101) is in dormant/idle mode fromthe cellular radio interface perspective. At step 302, the first smartdevice (101) connects to the second smart device (102) for example basedon either Bluetooth pairing protocol or WiFi association protocol toestablish the proximity connectivity. In step 303, the first smartdevice (101) provides the PLMN information concerning the PLMN on whichthe firs smart device (101) is registered along with dormant/idle modeoffload interest indication and assistance information.

If the registered PLMN of the second smart device (102) matches withthat of the first smart device (101) and at step 304 if the second smartdevice (102) decides to accept the offload interest indication fromfirst smart device (101) then the second smart device responds to thefirst smart device (101) with accept message. The offload acceptresponse is sent providing UE identity of the second smart device (102)along with accept indication at step 305. If the decision is reject thena reject indication is conveyed to the first smart device (101). Withthe reception of offload accept response at step 305 the first smartdevice (101) has successfully offloaded one or more idle mode functionsto second smart device (102). The various steps mentioned in FIG. 3illustrates the generalized alternative procedure for offload ofdormant/idle mode operation from the first smart device to the secondsmart using the proximity radio interface; therefore either some of thesteps can be combined, sequence of some steps can be modified or somesteps can be omitted without deviating from the spirit of theillustrated procedure.

FIG. 4 illustrates a message sequence flow 400 depicting an alternativemethod for the network controlled offload of dormant/idle mode operationfrom a first smart device (101) to a second smart device (102). All thesteps shown in message sequence flow 400 are similar to the steps shownin message sequence flow 200 except step 405, 406 and 407. At step 405,the first smart device (101) verifies the registered PLMN of the secondsmart device (102) and if the first smart device (101) matches with thefirst smart device own registered PLMN then the cellular radio of firstsmart device (101) transitions to active/connected mode fromdormant/idle mode. At step 406, the first smart device (101) sends idlemode offload request message to the cellular network (103) including theUE identity provided by the second smart device (102).

The UE identity concerning the second smart device can be for examplethe IMSI or GUTI associated with second smart device (102). The UEidentity associated with the second smart device (102) can be any UEidentity which the cellular network (103) can understand and identifythe second smart device (102). If the cellular network (103) accepts theoffload request then the cellular network (1030 responds to the firstsmart device (101) with offload response message in step 407. Theoffload response message includes the accept indication. If the decisionis reject then a reject indication is conveyed to the first smart device(101) in the offload response message. The offload request/responsemessages can be NAS messages and the decision to allow/dis-allow idlemode offload is taken by the MME in the cellular network (103). Based onthe UE identity of the second smart device (102) which the cellularnetwork (103) can understand and identify the second smart device (102),the cellular network (103) can determine the authenticity of anyprocedure carried out by the second smart device (102) on behalf of thefirst smart device (101). At step 408, the cellular radio of first smartdevice (101) transitions from active/connected mode to dormant/idle modeand completes the rest of the procedure to offload idle mode operationsto the second smart device (102). The various steps mentioned in FIG. 4illustrates the generalized network controlled procedure for offload ofdormant/idle mode operation from the first smart device to the secondsmart device; therefore either some of the steps can be combined,sequence of some steps can be modified or some steps can be omittedwithout deviating from the spirit of the illustrated procedure.

FIG. 5 illustrates a message sequence flow 500 depicting the trackingarea update procedure performed by a second smart device (102) on behalfof a first smart device (101). At step 501, the procedure to offloadidle mode operations to the second smart device (102) is performed bythe first smart device (101) using any of the methods shown in FIG. 2,FIG. 3 or FIG. 4. At step 502 a and step 502 b, the first smart device(101) and the second smart device (102) are in dormant/idle mode fromthe cellular radio interface perspective. At step 504, the first smartdevice (101) store the first smart device's NAS context associated withthe cellular radio and turn OFF the cellular radio while keeping theproximity radio activated and associated with the second smart device(102). The proximity radio of the first smart device (101) periodicallykeeps checking the pairing/association status with proximity radio ofthe second smart device (102) on the proximity radio interface. At step503, the second smart device (102) whose cellular radio is indormant/idle mode performs one or more dormant/idle functions such aspaging monitoring, cell-reselection, performing tracking area update iftriggered by NAS layer and device-to-device (D2D) operations accordingto procedures specified in 3GPP TS 36.304.

On reception of the assistance information from the first smart device(101) the second smart device (102) creates dormant/idle mode context ofthe first smart device (101).

Assuming the second smart device (102) is performing cell re-selectiondue to idle mode mobility which requires the cellular radio of thesecond smart device (102) to acquire system information of re-selectedcell. Since the first smart device (101) is paired/associated with thesecond smart device (102), it may be assumed the re-selected cell by thesecond smart device (102) would be potential cell for camping for thefirst smart device (101) if the second smart device (102) turns ON thecellular radio. From the system information of the re-selected cell thesecond smart device (102) receives the tracking area code (TAC) which isprovided to the NAS layer of cellular radio of second smart device(102). Based on the received TAC the NAS layer may trigger the trackingarea update (TAU) for the second smart device (102) according to thecriteria specified in 3GPP TS 24.301. At step 505, if the tracking areaupdate is triggered by the NAS layer based on the TAC received fromaccess stratum layer (AS) then the cellular radio transition fromdormant/idle mode to active/connected mode to perform the TAU procedure.This includes performing random access on the re-selected cell andestablishing RRC connection and sending the NAS message i.e trackingarea update (TAU) request message to the cellular network (103) in step506.

The TAU request message includes the contents for the second smartdevice (102) for example the mandatory parameter GUTI (User Equipmentidentity at MME level) for second smart device (102) and many otheroptional parameters. This TAU request message may be sent using the NASsecurity context of the second smart device (102) i.e as NAS PDUintegrity protected by the NAS integrity key of the second smart device(102). This TAU message may include a flag to indicate to the cellularnetwork (103) that the TAU request message also include contents for aplurality of first smart devices. The first smart device (101) contentsincluded in the TAU request message includes the GUTI of first smartdevice (101), a message authentication code (MAC-i) generated using theNAS integrity key associated with the first smart device (101) and someoptional parameters like the parameters of the paging cycle of the firstsmart device (101). The assistance information received from the firstsmart device (101) during the offload includes at least: the UE identityassociated with first smart device (101), list of MAC-i, paging cycleparameters and other information. This TAU request message thereforepiggybacks the TAU contents for first smart device (101) when TAU istriggered by NAS layer of the second smart device (102). The TAUpiggyback flag in TAU request message may indicate to the cellularnetwork (103) that the TAU message also includes TAU contents for aplurality of first smart devices. Based on the GUTI and MAC-i associatedwith the first smart device (101) the cellular network (103) canauthenticate the first smart device (101) and trust the TAU contentsassociated with the first smart device (101) if the offloaded idle modeoperation is not network controlled. In the alternative where the idlemode operation is network controlled, then there is no need to includethe MAC-i associated with the first smart device (101) in the TAUrequest message because the cellular network (103) has prior knowledgethat second smart device (102) may perform some procedures with thecellular network (103) on behalf of first smart device (101).

At the cellular network (103) if the GUTI associated with first smartdevice (101) is not identified by the MME handling the second smartdevice (102) then the GUTI associated with first smart device (101) isforwarded to appropriate MME based on the MME identifier (MMEI) in theGUTI. The MMEI shows which MME allocates the GUTI and an M-TMSI, atemporary value that uniquely identifies the first smart device (101) inthat particular MME. Based on the MME interaction at the cellularnetwork (103) the MME updates the location registration for the secondsmart device (102) and the first smart device (101). If there is MMEre-location for the first smart device (101) then possibly a new GUTI isallocated to the first smart device (101). MME re-location may alsoresult in refresh of the NAS security key associated with the firstsmart device (101). At step 507, the MME sends the TAU accept message tothe second smart device (102) which may include updated NAS informationfor the second smart device (102) and for a plurality of first smartdevices. At step 508, the NAS information associated with the secondsmart device (102) is updated and also the NAS information associatedwith the plurality of first smart devices is updated. The new NASinformation is updated in the dormant/idle mode context of the firstsmart device (101) maintained in the second smart device (102).

The cellular radio of second smart device (102) transitions todormant/idle mode from active/connected mode. If the dormant/idle modecontext associated with the first smart device (101) maintained in thesecond smart device (102) is updated then an event is triggered for thefirst smart device at step 509. A NAS Context container to update theNAS information is sent by the second smart device (102) to the firstsmart device (101) on the proximity radio interface at step 510 andthereafter at step 511 as an inter-radio message. At step 512, the firstsmart device (101) just updates the stored NAS context with the newinformation received in the NAS Context container without turning ON thecellular radio. Example of new NAS information could be updated pagingcycle parameters for the first smart device (101) or new GUTI for firstsmart device (101) which does not need the first smart device (101) toturn ON the cellular radio. For successive TAU request sent to thecellular network (103) on behalf of the first smart device (101), aunique MAC-i needs to be included for each TAU request message alongwith the TAU contents associated with first smart device (101). Thesecond smart device (102) receives a list of MAC-i from the first smartdevice (101) as assistance information and therefore on exhausting thelist of MAC-i the second smart device (102) can request a new list forMAC-i from the first smart device (101). The various steps mentioned inFIG. 5 illustrates the generalized tracking area update procedureperformed by second smart device on behalf of the first smart device;therefore either some of the steps can be combined, sequence of somesteps can be modified or some steps can be omitted without deviatingfrom the spirit of the illustrated procedure.

FIGS. 6A and 6B illustrate a message sequence flow 600 depicting thetracking area update procedure performed by a second smart device (102)on behalf of a first smart device (101) and there is need to update theNAS security context associated with cellular radio of the first smartdevice (101). All the steps shown in message sequence flow 600 aresimilar to the steps shown in message sequence flow 500 except that inthe TAU accept message in step 607 there is an indication to refresh theNAS security key associated with the first smart device in addition toupdate of the NAS information associated with the first smart device(101). For example if a new GUTI is allocated to the first smart device(101) due to MME re-location and if refresh of NAS security keyassociated with the first smart device (101) is decided by the cellularnetwork (103) then a NAS key refresh indication associated with thefirst smart device (101) is sent to second smart device (102) in the TAUaccept message in step 607. In such scenario after updating the NAScontext for plurality of device(s) the second smart device (102)transition to dormant/idle mode at step 608 and a trigger event for thefirst smart device (101) is generated at step 609.

The trigger event leads to sending the context transfer container to thefirst smart device (101) on the proximity radio interface including theevent trigger cause value. In this case the event trigger cause value isthe indication for refresh of the NAS security key associated with thefirst smart device (101). The context transfer message is sent throughthe inter-radio messages 610 and 612 respectively and on the proximityradio interface as context transfer container at step 611 which includesassistance information from the second smart device in addition to thetrigger event cause value. At step 614 on the receiving the triggerevent cause value associated with refresh of NAS security key, the firstsmart device (101) updates the stored NAS context with the newinformation received in the context transfer container and turns ON thecellular radio. Further, the assistance information received from thesecond smart device (102) may include some system information parametersassociated with the cell on which the second smart device (102) iscamped. The first smart device (101) camps on a suitable cell and speedsup the camping based on the received system information parameters fromthe second smart device (102). At step 615, the first smart device (101)transition to active/connected mode which involves performing randomaccess on the camped cell, establishing RRC connection with the cellularnetwork (103) and sending the NAS message to refresh the NAS securitycontext at step 616. The various steps mentioned in FIG. 6 illustratesthe generalized tracking area update procedure performed by the secondsmart device on behalf of the first smart device and there is need toupdate the NAS security context associated with first smart device;therefore either some of the steps can be combined, sequence of somesteps can be modified or some steps can be omitted without deviatingfrom the spirit of the illustrated procedure.

FIGS. 7A and 7B illustrate a message sequence flow 700 depicting thepaging monitoring procedure performed by a second smart device (102) onbehalf of a first smart device (101) which has offloaded thedormant/idle mode operation. All the steps shown in message sequenceflow 700 are similar to the steps shown in message sequence flow 500until step 704. Based on the assistance information sent by the firstsmart device (101) to the second smart device (102) as shown in step 207as depicted in FIG. 2, the second smart device (102) shall be able tomonitor paging on behalf of first smart device (101) when there is pagebroadcast from the cellular network (103) at step 705. The cellularnetwork (103) is able to send the page for first smart device (101) atstep 705 in the area where the second smart device (102) is locatedbased on the tracking area update procedure performed by the secondsmart device (102) on behalf of first smart device (101).

The assistance information for paging channel monitoring includes theparameters for paging cycle associated with first smart device (101) andthe user equipment (UE) identity associated with first smart device(101). The UE identity associated with the first smart device can be atleast one of: the IMSI and/or S-TMSI associated with the first smartdevice (101), the UE identity hashed by a hashing function and the GUTIassociated with the first smart device (101). Based on the paging cycleparameters and the UE identity in the form of IMSI, the second smartdevice (102) can determine the paging frame and the paging opportunityassociated with the first smart device (101) based on the equationspecified in 3GPP specification TS 36.304. Once the paging frame andpaging opportunity associated with first smart device (101) isdetermined then the second smart device shall be able to detect pagerecord for the first smart device (101) sent by the cellular network(103) on the paging channel at step 706. If a page record addressed tothe UE identity matches with the UE identity associated with first smartdevice (101) shared with second smart device (102) then at step 707 anevent trigger is detected for the first smart device (101). Apart fromthe page record for mobile terminated call for the first smart device(101) the paging message may include at least notification for systeminformation modification, indication for natural disaster like ETWS,CMAS notification.

The trigger event leads to sending the context transfer container to thefirst smart device (101) on the proximity radio interface including theevent trigger cause value. In this case the event trigger is theindication for one of: network page for the first smart device (101) fora mobile terminated call, system information modification cause value,ETWS notification cause value, CMAS notification cause value. Thecontext transfer message is sent through the inter-radio messages 708and 710 respectively and on the proximity radio interface as contexttransfer container at step 709. The context transfer container includesassistance information from second smart device (102) in addition to theevent trigger cause value. At step 712 on the receiving, the eventtrigger cause value associated with network page, the first smart device(101) updates the stored NAS context with any new information receivedin the context transfer container and turns ON the cellular radio.Further, the assistance information received from the second smartdevice (102) may include some system information parameters associatedwith the cell on which the second smart device (102) is camped. If theevent trigger cause value is mobile terminated call then the page recordfor the first smart device (101) detected by the second smart device(102) is included in the context transfer container. The first smartdevice (101) camps on a suitable cell and speeds up the camping based onthe received system information parameters from the second smart device(102). At step 713, the first smart device (101) transition toactive/connected mode which involves performing random access on thecamped cell, establishing RRC connection with the cellular network (103)and responding to network page if the event trigger cause value ismobile terminated call.

If event trigger cause value is system information modification or ETWSnotification or CMAS notification then after camping on a suitable cellor acceptable cell the first smart device performs the necessary actionsas specified in 3GPP specification TS 36.331 after reception of pagingmessage. In an alternative instead of sharing the IMSI directly as theUE identity associated with the first smart device (101), the UEidentity in the form of IMSI mod 1024; wherein the mod indicates modulooperation; can be shared with the second smart device (102) foridentifying the paging frame of the first smart device. The hashedIMSI/S-TMSI or the S-TMSI can be shared with the second smart device(102) to identify the page record associated with the first smart device(101). Within the paging frame which corresponds to a radio framecomprising 10 subframes; there is at most one paging opportunity for acellular device. The first smart device (101) may provide information onthe paging opportunity corresponding to the subframe number within thepaging frame to the second smart device (102). The various stepsmentioned in FIG. 7 illustrates the generalized the paging monitoringprocedure performed by the second smart device on behalf of the firstsmart device; therefore either some of the steps can be combined,sequence of some steps can be modified or some steps can be omittedwithout deviating from the spirit of the illustrated procedure.

FIG. 8 illustrates a message sequence flow 800 depicting the actionstaken by first smart device (101) on detecting an event trigger; whereinthe event trigger concerns breaking (losing) the proximity radioconnectivity between the first smart device (101) and the second smartdevice (102). At step 801, the procedure to offload idle mode operationsto the second smart device (102) is successfully completed by firstsmart device (101) using any of the methods shown in FIG. 2, FIG. 3 orFIG. 4. The two smart devices are either paired based on the Bluetoothproximity radio interface or associated based on the WiFi proximityradio interface. During the course of time it may be possible that theproximity radio interface between the two smart devices is broken due tosome reason like two device moving out of the coverage range ofproximity radio interface. At step 805, if un-pairing or dis-associationwith proximity radio of the second smart device (102) is detected byproximity radio of the first smart device (101) then at step 806 anevent trigger associated with proximity radio interface un-pairingand/or dis-association is generated. The trigger event leads to sendinga cellular radio ON indication at step 807 from the proximity radio tothe cellular radio through the radio layer interface of the first smartdevice (101). On the receiving the cellular radio ON indication at step808 the first smart device (101) turns on the cellular radio andperforms cell selection procedure according to 3GPP TS 36.304 to camp ona suitable or acceptable cell.

FIGS. 9A and 9B illustrate a message sequence flow 900 depicting one ormore idle mode functions performed by a second smart device (102) onbehalf of a first smart device (101) wherein the second smart device isin active/connected mode. The tracking area update procedure and pagingmonitoring procedure described in FIG. 5, FIG. 6 and FIG. 7 areperformed by the second smart device (102) on behalf of the first smartdevice (101); wherein the second smart device is in dormant/idle mode.The cellular radio of second smart device (102) monitors pagingregardless of the state of radio either dormant/idle mode oractive/connected mode. When the second smart device (102) is inactive/connected mode the paging message can indicate system informationmodification, notification for CMAS, notification for ETWS. However, ifthere is a mobile terminated call for the first smart device (101) thenthe paging message can include the page record for the first smartdevice (101). Therefore, even when the second smart device (102) is inactive/connected mode the second smart device (102) may be able tomonitor paging and detect paging record for mobile terminated callassociated with the first smart device (101).

Tracking area update is triggered by NAS layer based on the TAC providedby AS layer to NAS layer based on conditions specified in 3GPP TS24.301. The cellular radio of the second smart device (102) acquiressystem information from time to time depending on mobility and otherconditions regardless of the state of cellular radio either dormant/idlemode or active/connected mode. Therefore, the offload of idle modeoperation of the first smart device (101) is also feasible when thecellular radio of the second smart device (102) is in active/connectedmode. At step 903, this is reflected as performing functions likemonitoring paging in active/connected mode, performing handoversdepending on mobility conditions and performing tracking area updates.Rest all the steps depicted in FIG. 9 are similar to steps shown in FIG.5, FIG. 6 and FIG. 7. It is possible to that the steps shown in FIG. 9are not performed in the same sequence as depicted and some of the stepsmay not be triggered if the event trigger for the first smart device isnot detected. The various steps mentioned in FIG. 9 illustrates one ormore idle mode functions performed by second smart device on behalf offirst smart device wherein the second smart device is inactive/connected mode; therefore either some of the steps can becombined, sequence of some steps can be modified or some steps can beomitted without deviating from the spirit of the illustrated procedure.

FIGS. 10A and 10B illustrate a flow chart sequence 1000 describing thedetailed operation of a first smart device (101) for the offload of oneor more idle mode functions associated with the cellular radiocapability. At step 1001, the first smart device (101) pairs orassociates using Bluetooth or WiFi proximity radio interface with asecond smart device (102) having cellular radio capability. During thepairing or association the first smart device (101) performs mutualauthentication with the second smart device (102) through proximityradio interface. The cellular radio state associated with the firstsmart device (101) is either dormant or idle mode from the cellularradio interface perspective. At step 1002, the first smart deviceobtains UE identity associated with second smart device and PLMNinformation associated with second smart device concerning the PLMN onwhich second smart device is registered. After verifying the receivedPLMN information a check is performed with the registered PLMNinformation associated with the first smart device at step 1003. If theregistered PLMN information of both the devices is same then the firstsmart device sends offload request including assistance information tothe second smart device at step 1004.

If network controlled idle mode offload is desired then before sendingoffload request to second smart device an offload indication is sent thecellular network including the UE identity associated with second smartdevice. Further message exchange for offload of idle mode is performedwith the second smart device upon reception of permission from thecellular network. Alternatively, at step 1002, the first smart devicemay send offload request with PLMN information concerning the PLMN onwhich the first smart device is registered, offload interest indication,assistance information to the second smart device and in responsereceives offload accept message from the second smart device at step1003. At step 1005, upon reception of Offload Accept Response from thesecond smart device over secured proximity interface; the first smartdevice store the NAS context associated with the cellular radio and TURNOFF radio and a baseband circuitry associated with cellular radiocapability. Upon offload of idle mode functions to the second smartdevice; the first smart device periodically monitors if pairing and/orassociation is maintained with the second smart device over a proximityradio interface at step 1006.

In case, if pairing and/or association over proximity radio interface isdetected to be broken between the first smart device and the secondsmart device then the flow control moves to step 1011 wherein the firstsmart device TURNS ON radio and baseband circuitry associated withcellular radio capability and camp on one of suitable cell or acceptablecell. If pairing and/or association over proximity radio interface ismaintained between the first smart device and the second smart devicethen at step 1007 the first smart device checks for context transferindication from the second smart device over the proximity radiointerface. At step 1008, the first smart device updates the stored NAScontext using new NAS information received from the second smart deviceif context transfer indication is received at step 1007 else the flowcontrol moves to periodically check the pairing status at step 1006. Atstep 1009, the first smart device checks if any event trigger causevalue is associated with context transfer indication. If event triggercause value is received then subsequent action is triggered depending onthe cause value of trigger event at step 1010. One of the actions atstep 1011 is to TURN ON radio and baseband circuitry associated withcellular radio capability and camp on one of suitable cell or acceptablecell using assistance information received from second smart device ifincluded along with event trigger cause value. In case, if event triggercause value concerns mobile terminated call for the first smart deviceor event trigger cause value concerns NAS security refresh for the firstsmart device then the cellular radio transition to active/connected modeand respond to network page and/or refresh NAS security at step 1012.The flow sequence described in FIG. 10 illustrates detailed operation ofthe first smart device for the offload of one or more idle modefunctions associated with the cellular radio capability; thereforeeither some of the steps can be combined, sequence of some steps can bemodified or some steps can be omitted without deviating from the spiritof the illustrated operation.

FIGS. 11A, 11B and 11C illustrate a flow chart sequence 1100 describingdetailed operation of a second smart device when a cellular radio of asecond smart device acts as proxy for one or more idle mode functionsassociated with the cellular radio capability of first smart device. Atstep 1101, the second smart device is paired/associated with at leastone or plurality of first smart device(s) after respective mutualauthentication through respective proximity radio interfaces. Thecellular radio state associated with the second smart device is one of:active/connected mode or dormant/idle mode. At step 1102, the secondsmart device, send PLMN information associated with the second smartdevice concerning the PLMN on which the second smart device isregistered upon receiving PLMN request from at least one or plurality ofthe first smart device(s) through respective proximity radio interfaces.The second smart device also sends UE identity associated with thesecond smart device to at least one or a plurality of the first smartdevices through respective proximity radio interfaces. At step 1103, thesecond smart device receive Offload Request along with assistanceinformation from the first smart device through secured proximity radiointerface.

After receiving offload request the second smart device decide whethercellular radio of the second smart device can act as proxy for one ormore idle mode functions associated with the cellular radio capabilityof the first smart device at step 1104. The decision may be positivedepending on internal logic of the second smart device. There issufficient battery power at disposal then the second smart device sendsoffload accept response to identified the first smart device onproximity radio interface at step 1104. If the decision is negativebecause battery power of the second smart device is weak then thesecondary smart device may send offload reject response over proximityinterface at step 1114. In case, if the second smart device sendsoffload accept response to identified first device at step 1104 then thesecond smart device store assistance information received from the firstsmart device in a context associated with the first smart deviceregardless of cellular radio state (i.e. either active/connected mode ordormant/idle mode) associated with the second smart device at step 1105.At step 1105, the second smart device perform functions related topaging channel monitoring, mobility evaluation, tracking area for thesecond smart device and on behalf of plurality of first smart device(s),D2D operation on behalf of a plurality of first smart devices based oninformation stored in the context of first smart device.

In case of any change in Tracking area is detected by NAS layerassociated with the second smart device at step 1107 then a second smarttransition to active/connected mode (if in dormant/idle mode) andperform tracking area update procedure with the cellular network for thesecond smart device and a plurality of first smart devices at step 1108.The flow control moves to step 1110 to check if any event triggercondition is met based on the TAU accept message received from thecellular network. In case the TAU accept message contains only fresh NASinformation without any indication for NAS security refresh for thefirst smart device then at step 1111 the second smart device send NASinformation update to plurality of the first smart devices on respectiveproximity interface. At step 1109, the second smart device monitor thepaging channel for the second smart device and on behalf of a pluralityof the first devices based on the assistance information provided byrespective the first smart device(s). In case, if the second smartdevice detects page indication for the plurality of first smart devicesthen at step 1111 an event trigger is generated with appropriate causevalue. Similarly, if the TAU accepts message includes an indication forNAS security refresh for the first smart device then at step 1111 andevent trigger is generated with appropriate cause value. At step 1112the second smart device sends Context Transfer indication along withevent trigger cause value and assistance information to at least onefirst smart device on respective proximity radio interface. At step1113, the second smart device also releases context associated with thefirst smart device to which context transfer indication is sent. Theflow sequence described in FIG. 11 illustrates detailed operation of thesecond smart device when the cellular radio of the second smart deviceacts as proxy for one or more idle mode functions associated with thecellular radio capability of the first smart device; therefore eithersome of the steps can be combined, sequence of some steps can bemodified or some steps can be omitted without deviating from the spiritof the illustrated operation.

FIG. 12 illustrates a depiction of block diagram 1200 comprising thenecessary hardware and software modules of a first smart device and asecond smart device to realize the methods disclosed in the inventionfor offload of one or more idle mode functions. The primary blockspresent in the first and second smart device includes a proximity radiointerface 1210, a radio interface layer 1220, a cellular radio interface1230, a processor 1240, a battery 1250, a memory 1260 and a display1270.

The proximity radio interface 1210, which is a low power radio could bebased on Bluetooth standard, WI FI standard or LTE based ProSeinterface. The proximity radio interface 1210 contains all the necessaryhardware and software components to perform baseband and radiooperations such as pairing, discovery, association, data exchange on theproximity interface established with another proximity radio of samekind.

The radio interface layer 1220 acts as the coordinator between theproximity radio interface 1210 and cellular radio interface 1230 tohandle the inter-radio messages. The information from the cellular radiointerface 1230 is included in a container prepared by the radiointerface layer and passed as application data to the proximity radiointerface 1210. The container received from proximity radio interface1210 is converted into appropriate access stratum information andnon-access stratum information and passed on to the cellular radiointerface 1230.

In an embodiment, the radio interface layer is configured to communicateinter-radio messages between the proximity radio interface and thecellular radio interface.

The cellular radio interface 1230 consist of all the necessary hardwareand software components to perform baseband, radio and protocolprocessing related operations on the interface with the cellularnetwork. These operations are divided between the access stratum layerand Non access stratum layer. The cellular radio interface could bebased on LTE standard, UMTS standard, CDMA standard or any othercellular radio access technology. For example, the access stratum layerin the cellular radio interface 1230 in the smart device can beconfigured to receive the synchronization signal and system informationfrom the cellular network to perform cell selection and cellre-selection. Further, the access stratum layer can be configured toperform random access procedure on the selected cell of the cellularnetwork. Further, the cellular radio interface 1230 can be configured totransmit and receive data from the cellular network 103 according tophysical layer waveform and coding specified for concerned radio accesstechnology eg. IMT Advanced system specified by 3 GPP specification.Similarly the non-access stratum in the cellular radio interface 1230can be configured to transmit and receive tracking area update requestand accept messages and other NAS level messages to and from thecellular network according to protocol level messages specified for theconcerned radio access technology.

The processor 1240 depicts a computing environment in the smart device(101/102) for implementing a method and system for offload of one ormore idle mode functions according to the embodiments as disclosedherein. The computing environment of 1240 comprises at least oneprocessing unit that is equipped with a control unit and an ArithmeticLogic Unit (ALU), a clock chip, plurality of networking devices, and aplurality Input output (I/O) devices. The processor 1240 is responsiblefor processing the instructions of the algorithm. The processing unitreceives commands from the control unit in order to perform itsprocessing. Further, any logical and arithmetic operations involved inthe execution of the instructions are computed with the help of the ALU.The overall computing environment can be composed of multiplehomogeneous or heterogeneous cores, multiple CPUs of different kinds,special media and other accelerators.

The processing unit is responsible for processing the instructions ofthe algorithm. The algorithm comprising of instructions and codesrequired for the implementation are stored in either the memory 1260 orthe storage unit or both. At the time of execution, the instructions maybe fetched from the corresponding memory 1260 or storage unit, andexecuted by the processing unit. The processing unit synchronizes theoperations and executes the instructions based on the timing signalsgenerated by the clock chip. The embodiments disclosed herein can beimplemented through at least one software program running on at leastone hardware device and performing management functions to control theelements. The methods shown in the FIGS. 10 and 11 include variousunits, blocks, modules, or steps described in relation with methods,processes, algorithms, or systems of the present invention, which can beimplemented using any general purpose processor and any combination ofprogramming language, application, and embedded processor.

The battery 1250 in the smart device (101/102) is responsible forpowering the various modules as depicted in the block diagram 1200. Thebattery hosts the battery wherein the battery is similar to the batteryseen in smartphones or other smart devices like smartwatch whichrequires regular charging from a power source. One of the mainmotivations of the method for offload of one or more idle mode functionsaccording to the embodiments as disclosed herein is to save batterypower consumption in a smart device wherein the battery standby time islow. By implementing the disclosed methods in the respective devices thestandby time of battery of the first smart device can be significantlyimproved.

Further, the memory 1260 is also configured to store information relatedto smart device operation. The memory 1260 can be configured to storeNAS information, assistance information exchanged between the devices,etc.

The display 1270 in the smart device (101/102) can be configured so thatuser can input information or information can output on the display forthe user to understand some smart device operations when the smartdevice is performing offload operations. Most of the offload operationsare transparent to the user and may not need user input nor output onthe display. However, the mutual authentication between the proximityradios of the involved devices may require user input or output throughthe display.

In an embodiment at least one first smart device having cellular radiocapability and proximity radio capability when in dormant/idle mode withrespect to cellular interface offload one or more dormant/idle modefunctions using a secured proximity radio interface to a second smartdevice having cellular radio capability and proximity radio capability;wherein the first smart device and the second smart device belong to thesame registered PLMN. In an embodiment a mutual authentication procedureis performed between the first smart device and the second smart devicethrough the proximity interface to develop mutual trust; before thefirst smart device start offload of one or more dormant/idle modefunctions to the second smart device through secured proximityinterface. In an embodiment, offload of one or more dormant/idle modefunctions from the first smart device to the second smart deviceincludes sending an offload indication to the cellular networkcontaining identity associated with the second smart device; wherein thefirst smart device and the second smart device belong to the sameregistered PLMN.

In an embodiment, offload of one or more dormant/idle mode functionsfrom the first smart device to the second smart device includes sendingoffload request message containing assistance information from the firstsmart device. In an embodiment, assistance information included inoffload request message from the first smart device includes at least:identity information associated with the first smart device known to thenetwork, UE capability information in terms of frequency bands supportedby the first smart device, the parameters for paging cycle associatedwith first smart device, list of Message Authentication Code for NAScalculated using the NAS integrity key associated with the first smartdevice and other information like index of hashing function. In anembodiment, the first smart device turns OFF the first smart device'scellular radio capability upon offload of one or more dormant/idle modefunctions using secured proximity radio interface to the second smartdevice having cellular radio capability and proximity radio capabilityuntil a time period wherein the first smart device and the second smartdevice are paired/associated with each other through the securedproximity interface. In an embodiment a dormant/idle mode offloadoperation associated with the cellular radio capability of the secondsmart device includes monitoring paging channel in dormant/idle mode fornetwork page for the second smart device and on behalf of at least thefirst smart device having cellular radio capability; wherein the firstsmart device shares assistance information with the second smart devicebelonging to the same registered PLMN.

In an embodiment an active/connected mode operation associated with thecellular radio capability of a second smart device includes performingupdate of registration area for the second smart device and on behalf ofat least a first smart device having cellular radio capability; whereinthe second smart device when in dormant/idle receives tracking area codeinformation from system information broadcast which when forwarded toNAS layer triggers tracking area update during idle mode mobilityassociated with the second smart device.

In an embodiment the UE identity information shared between the smartdevices is at least one of the IMSI, S-TMSI, GUTI, hashed IMSI, IMSI mod1024. In an embodiment the paging opportunity within the paging frame ofthe concerned smart device is shared as a subframe index correspondingto the number of subframes within the radio frame.

In an embodiment a first smart device just updates stored NAS contextassociated with radio access technology belonging to the cellular radiocapability of the first smart device keeping cellular radio OFF uponreceiving new NAS information from the second smart device. In anembodiment the first smart device turns ON its cellular radio capabilityand immediately camps on at least one of: a suitable cell and anacceptable cell associated with radio access technology belonging to thecellular radio capability of the first smart device upon receiving oneof triggering event associated with the first smart device.

In an embodiment a second smart device releases the dormant/idle modecontext associated with at least a first smart device upon detecting oneof triggering event associated with the first smart device and notifyingthe triggering event to the first smart device through the securedproximity interface.

In an embodiment a triggering event associated with the first smartdevice includes sending a context transfer indication from the secondsmart device through secured proximity interface along with the eventtrigger cause value.

In an embodiment context transfer indication includes event triggerassociated with one of: page for first smart device wherein the eventtrigger cause value indicates either mobile terminated call or systeminformation modification or ETWS notification or CMAS notification andevent trigger cause value for NAS security refresh for the first smartdevice.

In an embodiment a triggering event associated with the first smartdevice includes detecting by proximity radio of first smart deviceun-pairing/dis-association of the first smart device and the secondsmart device on the proximity interface and sending an indication toTURN ON the cellular radio of the first smart device.

In an embodiment the TAU request message sent by the second smart devicemay include a flag to indicate to the cellular network that the TAUrequest message also include TAU contents for a plurality of devices. Inan embodiment the TAU contents for a plurality of devices includes theUE identity in the form of GUTI associated with the device, the MAC-igenerated using the NAS integrity key associated with the device.

In an embodiment, assistance information included along with contexttransfer indication from a second smart device comprises one of: pagerecord information associated with first smart device, update to the NASinformation associated with a first smart device, and other informationlike system acquisition information related to a plurality of candidatecells. In an embodiment, system acquisition information related to theplurality of candidate cells is included in the context transferindication from the second smart device to assist the first smart deviceto camp on at least one of: a suitable cell and an acceptable cellassociated with radio access technology belonging to the cellularcapability and UE capability of the first smart device.

In an embodiment operation of a second smart device having cellularradio capability includes monitoring paging channel in eitheractive/connected mode or dormant/idle mode for network page for thesecond smart device and on behalf of at least one first smart devicehaving cellular radio capability; wherein the first smart device sharesassistance information related to page monitoring with the second smartdevice belonging to the same registered PLMN.

In an embodiment operation of a second smart device having cellularradio capability includes performing update of registration area withthe cellular network for the second smart device and on behalf of atleast one first smart device by including at least: a flag indicatingthe tracking area update request is on behalf of at least one firstsmart device, identity information associated with the first smartdevice and message authentication code for NAS (NAS-MAC) associated withthe first smart device; wherein the first smart device shares assistanceinformation with the second smart device belonging to the sameregistered PLMN. In an embodiment NAS layer of second smart devicedetermines tracking area code has changed during either active/connectedmode mobility or dormant/idle mode mobility associated with the secondsmart device to perform update of registration area with the cellularnetwork for the second smart device and on behalf of at least one firstsmart device.

In an embodiment operation of a second smart device having cellularradio capability includes performing D2D operations such as transmit orreceive ProSe direct communication in dormant/idle mode for the secondsmart device and on behalf of at least a first smart device havingcellular radio capability; wherein the first smart device sharesassistance information with the second smart device belonging to thesame registered PLMN.

In an embodiment the second smart device can be a multi SubscriberIdentity Module (SIM) device. In an embodiment the second smart deviceuses the protocol stack corresponding to SIM from a plurality of SIMssuch that the PLMN selected by the second smart device is the same PLMNas first smart device. In an embodiment a multi SIM second smart devicemay be handling dormant/idle operations of one or more first smartdevices on a first SIM and handling one or more first smart devices on asecond SIM and so on.

In an embodiment operation of a second smart device having cellularradio capability includes monitoring paging channel in eitheractive/connected mode or dormant/idle mode for network page for thesecond smart device and on behalf of at least one first smart devicehaving cellular radio capability; wherein the first smart device sharesassistance information related to page monitoring with the second smartdevice belonging to different registered PLMN.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method of a first device, the methodcomprising: entering an idle mode of a cellular radio interface;performing a proximity connection with a second device using a proximityradio interface; receiving a registered public land mobile network(PLMN) of the second device from the second device; determining whetherthe registered PLMN of the second device is same as a registered PLMN ofthe first device; transmitting, to the second device, a first message torequest offloading an idle mode function for the first device, when theregistered PLMN of the second device is same as the registered PLMN ofthe first device; and receiving, from the second device, a secondmessage indicating that the second device accepts the request, inresponse to the first message.
 2. The method of claim 1, furthercomprising: transmitting, to a cellular network, a third message torequest offloading the idle mode function of the first device to thesecond device, wherein the third message includes identity of the seconddevice; and receiving a fourth message indicting that the idle modefunction of the first device is offloaded to the second device, inresponse to the third message.
 3. The method of claim 1, furthercomprising: receiving, from the second device, non-access stratum (NAS)context container using the proximity radio interface to update NASinformation of the first device if the first device detects an event toupdate the NAS information; and updating the NAS information of thefirst device.
 4. The method of claim 1, further comprising: receiving,from the second device, a context transfer container using the proximityradio interface if the second device detects an event trigger associatedwith the first device; updating NAS context based on informationincluded in the context transfer container; and turning on the cellularradio interface, and wherein the method further comprises: entering anactive mode of the cellular radio interface; and transmitting a responsemessage to a cellular network if the event trigger is associated withpage record for the first device.
 5. The method of claim 1, wherein theidle mode function of the first device comprises at least one of pagingmonitoring, cell re-selection, tracing area update, PLMN selection,device to device communication, or creating idle mode context of thefirst device.
 6. A method of a second device, the method comprising:performing a proximity connection with a first device using a proximityradio interface after the first device enters an idle mode of a cellularradio interface; transmitting a registered public land mobile network(PLMN) of the second device to the first device; receiving, from thefirst device, a first message to request offloading an idle modefunction for the first device to the second device, when the registeredPLMN of the second device is same as the registered PLMN of the firstdevice; and transmitting, to the first device, a second messageindicating that the second device accepts the request, in response tothe first message received from the first device.
 7. The method of claim6, further comprising: transmitting, to a cellular network, a trackingarea update (TAU) request message for the second device and the firstdevice if tracking area change is detected; receiving a TAU acceptmessage in response to the TAU request message, wherein the TAU acceptmessage includes NAS information for the second device and the firstdevice; updating an NAS context for the second device; and creating theNAS context associated with the first device, and wherein the methodfurther comprises: transmitting, to the first device, a NAS contextcontainer using the proximity radio interface to update the NASinformation of the first device.
 8. The method of claim 6, wherein theidle mode function of the first device comprises at least one of pagingmonitoring, cell re-selection, tracing area update, PLMN selection,device to device communication, or creating idle mode context of thefirst device.
 9. The method of claim 6, transmitting, to the firstdevice, a context transfer container using the proximity radio interfaceif the second device detects an event trigger associated with the firstdevice.
 10. The method of claim 6, further comprising: verifying theregistered PLMN of the second device; and deciding an offload operationrequested by the first device based on the verified registered PLMN. 11.A first device comprising: a transceiver; and a processor configured to:enter an idle mode of a cellular radio interface; perform a proximityconnection with a second device using a proximity radio interface;control the transceiver to receive a registered public land mobilenetwork (PLMN) of the second device from the second device; determinewhether the registered PLMN of the second device is same as a registeredPLMN of the first device; control the transceiver to transmit, to thesecond device, a first message to request offloading an idle modefunction for the first device, when the registered PLMN of the seconddevice is same as the registered PLMN of the first device; and controlthe transceiver to receive, from the second device, a second messageindicating that the second device accepts the request, in response tothe first message.
 12. The first device of claim 11, wherein theprocessor is further configured to: control the transceiver to transmit,to a cellular network, a third message to re request offloading the idlemode function of the first device to the second device , wherein therequest message includes identity of the second device; and control thetransceiver to receive a fourth message indicting that the idle modefunction of the first device is offloaded to the second device, inresponse to the third message.
 13. The first device of claim 11, whereinthe processor is further configured to: control the transceiver toreceive, from the second device, a non-access stratum (NAS) contextcontainer using the proximity radio interface to update NAS informationof the first device if the second device detects an event to update theNAS information; and updating the NAS information of the first device.14. The first device of claim 11, wherein the processor is furtherconfigured to: control the transceiver to receive, from the seconddevice, a context transfer container using the proximity radio interfaceif the second device detects an event trigger associated with the firstdevice; updating NAS context based on information included in thecontext transfer container; and turn on the cellular radio interface,and wherein the processor is further configured to: enter an active modeof the cellular radio interface; and control the transceiver to transmita response message to a cellular network if the event trigger isassociated with page record for the first device.
 15. The first deviceof claim 11, wherein the idle mode function of the first devicecomprises at least one of paging monitoring, cell re-selection, tracingarea update, PLMN selection, device to device communication, or creatingidle mode context of the first device.
 16. A second device comprising: atransceiver; and a processor configured to: perform a proximityconnection with a first device using a proximity radio interface afterthe first device enters an idle mode of a cellular radio interface;control the transceiver to transmit a registered public land mobilenetwork (PLMN) of the second device to the first device; control thetransceiver to receive, from the first device, a first message torequest offloading an idle mode function for the first device to thesecond device, when the registered PLMN of the second device is same asthe registered PLMN of the first device; and control the transceiver totransmit, to the first device, a second message indicating that thesecond device accepts the request, in response to the first messagereceived from the first device.
 17. The second device of claim 16,wherein the processor is further configured to: control the transceiverto transmit, to the cellular radio interface, a tracking area update(TAU) request message for the second device and the first device iftracking area change is detected; control the transceiver to receive aTAU accept message in response to the TAU request message, wherein theTAU accept message includes NAS information for the second device andthe first device; update an NAS context for the second device; andcreate the NAS context associated with the first device, and wherein theprocessor is further configured to: control the transceiver to transmit,to the first device, a NAS context container using the proximity radiointerface to update the NAS information of the first device.
 18. Thesecond device of claim 16, wherein the idle mode function of the firstdevice comprises at least one of paging monitoring, cell re-selection,tracing area update, PLMN selection, device to device communication, orcreating idle mode context of the first device..
 19. The second deviceof claim 16, wherein the processor is further configured to: control thetransceiver to transmit, to the first device, a context transfercontainer using the proximity radio interface if the second devicedetects an event trigger associated with the first device.
 20. Thesecond device of claim 16, wherein the processor is further configuredto: verify the registered PLMN of the second device; and decide anoffload operation requested by the first device based on the verifiedregistered PLMN.